Positioning of mobile devices in wireless networks is a challenge owing to the mobility of users and the dynamic nature of both the environments and radio signals. Positioning Quality of Services (QoS) is typically defined in ‘terms of accuracy, confidence level and the time it takes to obtain a positioning result. The current trend shows that the demands from users, network operators, service providers and regulatory bodies regarding positioning QoS are increasing.
In outdoor environments, position estimation can be done using e.g. global positioning systems, i.e. GNSS/GPS (Global Navigation Satellite System/Global Positioning System), or methods based thereon, such as Assisted-GPS (A-GPS). However, this requires that the user equipment (UE) is provided with additional functionality concerning e.g. reception of radio signals related to such positioning systems.
Position estimation can also be performed using the wireless network itself. Methods using the wireless network can be grouped in different groups. A first group comprises methods that are based on the identification of the radio cell to which a mobile terminal is connected, e.g. by using Cell ID (CID). In its simplest form, a UE is known to be situated within the coverage area of a certain base station if the UE is communicating with the wireless network through that base station. The accuracy can be improved by also taking into account information from so-called neighbor lists. However, the accuracy is even then not very impressive.
Another group of position estimation methods are based on measurements of signal propagation times or quantities related thereto. Timing Advance (TA) in Long Term Evolution (LTE) systems and Round Trip Time (RTT) in Wideband Code Division Multiple Access (WCDMA) systems are examples of such methods. Briefly, the travel time of radio waves from the Radio Base Station (RBS) to the UE and back is measured. By combining such information with propagation times to neighboring RBS's enabling triangulation calculations, the accuracy can be improved somewhat. However, this possibility only occurs in a limited part of the cells, typically less than 25%. The signal propagation time measurements can also be combined with Cell ID information. As for other terrestrial positioning methods, like Observed Time Difference of Arrival (OTDOA), these suffer from a too low detection performance to provide good enough performance, at least in the basic configuration.
Thus, there is a need for fast and reasonable accurate user device positioning algorithms in cellular mobile systems. Such algorithms should be non-GNSS/GPS based, preferably non-UE controlled and handled and processed in/by the network (i.e. by one or several evolved Node B (eNodeB)/radio base stations (RBS)), have a quick response time, meaning not requiring time consuming data processing, and provide a user location precision beneficial for typical positioning use cases (i.e. <<100 m).
A brief overview of existing positioning solutions shows a limited number of, or in fact, very few solutions capable of providing sufficient resolution.                CID—Cell ID: Position is determined from serving cell location.        E-CID—Enhanced Cell ID: Include information of timing advance (i.e. distance), possibly multiple cells, etc.        AoA—Angle of Arrival: Estimates the direction from the site to the mobile.        OTDOA/UTDOA—Observed/Uplink Time Difference of Arrival: Uses timing information from several cells to triangulate user positions.        Fingerprinting: Mapping radio frequency (RF) measurements onto an RF map based on predictions and/or controlled measurements.        A-GNSS—Assisted GNSS, e.g. GPS, GLONASS (Globalnaya Navigatsionnaya Sputnikova Sistema) and Galileo: Based on time differences in propagation from >3 satellites; requires more or less line-of-sight (LOS) to satellites.        Hybrid solutions: Combination of several methods.        